The present invention relates to a semiconductor device applied to an intelligent power module for an inverter apparatus, and more specifically, relates to an assembled structure.
First, an intelligent power module applied to an inverter apparatus will be described as an example of a conventional intelligent power module. An assembled structure of the example is shown in FIGS. 12(a) to 13(b).
In the figures, reference numeral 1 denotes a radiating metal base (a copper base), reference numeral 2 denotes an enclosure case composed of a molded resin integrated with terminals, and reference numeral 3 denotes main terminals (external lead terminals, or screw terminals, for input and output of a power circuit and for a brake circuit). Reference numeral 4 denotes control terminals (external lead terminals, or pin terminals, used to input and output control signals to and from a control circuit), reference numerals 5 and 6 denote a power circuit (a circuit assembly) and a control circuit (a circuit assembly), respectively, and reference numeral 7 denotes bonding wires (internal wiring).
In this case, the power circuit 5 is composed of a circuit board 5a having power semiconductor elements 5b such as IGBTs and free wheeling diodes 5c mounted thereon. The power circuit board 5a is a direct bonding copper substrate composed of a ceramic plate such as alumina or aluminum nitride with a copper circuit pattern directly bonded on a top surface and a copper layer directly bonded on a bottom surface of the ceramic plate, respectively. The control circuit 6 is composed of a printed circuit board 6a with various circuit components including ICs 6b that drive the power elements 5b mounted thereon.
In the assembled structure shown in FIGS. 12(a) and 12(b), the power circuit 5 and the control circuit 6 are mounted on a top surface of the metal base 1 parallel to each other and are assembled as follows: First, the power circuit 5 with the elements mounted thereon is soldered to the metal base plate 1 so that the copper layer of the circuit board 5a faces downward. Next, the printed circuit board 6a of the control circuit 6 with the elements mounted thereon is glued to the metal base plate 1 with adhesive. Subsequently, the bonding wires 7 are connected between the power circuit 5 and the control circuit 6 so as to provide internal wiring for these circuits. Then, the enclosure case 2 integrated with the terminals is placed on the metal base plate 1 and joined thereto with adhesive. Thereafter, the tips of inner leads 3a from the main circuit terminals 3, which project to the interior of the enclosure case 2, are soldered to a conductor pattern on the power circuit board 5a so as to be wired together internally.
Similarly, the control terminals 4 are soldered to the conductor pattern on the control circuit board 6a so as to be wired together internally. In this assembled state, a gel-like filler (for example, a silicone gel) is injected into the package to seal the power circuit 5 and control circuit 6. Finally, a top cover (not shown) is placed on the enclosure case 2 and is glued and fixed thereto.
In the assembled structure in FIGS. 13(a) and 13(b), the power circuit 5 and the control circuit 6 are integrated into the package in a manner of a two-story building. In this case, the power circuit 5 is soldered to the metal base plate 1 as in FIGS. 12(a) and 12(b), whereas the control circuit 6 is assembled as follows: The enclosure case 2 integrated with the terminals is placed on the metal plate 1 having the power circuit 5 mounted thereon, and the main circuit terminals 3 are soldered to the conductor pattern on the power circuit board 5a. Then, a relay terminal block 8 composed of a resin frame 8a molded integrally with terminal conductor pieces 8b is placed on the power circuit 5, and the terminal conductor pieces 8b are soldered to the conductive pattern on the power circuit 5. Then, the printed circuit board 6a of the control circuit 6 is placed on the relay terminal block 8, and then soldered to the terminal conductor pieces 8b and control terminals 4. Subsequently, as described in FIG. 12(b), a gel-like filler is injected into the package, and a top cover is finally placed on the package for assembly.
Conventional semiconductor devices having the assembled structure described previously have the following problems:
(1) In the configuration in FIG. 12(a) and 12(b), the power circuit 5 and the control circuit 6 are flush with each other. Accordingly, the package has a large occupied area, thereby increasing a size of the semiconductor device. Further, when a result of an intermediate product inspection, carried out during an assembly process of the power circuit 5 and the control circuit 6 installed on the metal base plate 1, indicates that any of the circuit components, such as the ICs 6b mounted on the printed circuit board 6a of the control circuit 6, is defective, since the printed circuit board 6a is firmly secured to the metal base plate 1 by adhesive, it is impossible to peel only the printed circuit board 6a off the metal base plate 1 to replace the defective component with a good one, and install the good printed circuit board 6a back into an assembly line. Consequently, the intermediate product assembly must be entirely disposed, thereby resulting in loss of the component.
(2) Further, the two-story building configuration in FIGS. 13(a) and 13(b) is advantageous as a size of the semiconductor can be reduced. Also, when an inspection result of an intermediate test carried out during the assembly process indicates that any of the components of the control circuit is defective, the defective component can easily be replaced with a good one. However, the conventional structure still has the following problems: First, the two-story structure increases an external height of the module. Further, when the control circuit 6, which has substantially the same shape as the power circuit 5, is assembled above the power circuit 5 inside the package, the power circuit 5 is hidden behind the control circuit 6 and becomes invisible from outside. Consequently, an internal structure of the package can not be checked. Furthermore, when the gel-like filler is injected into the package, an injection process takes long time because only a narrow space is left between the enclosure case 2 and a periphery of the printed circuit board 6a of the control circuit 6.
Moreover, to connect the power module and a peripheral circuit (an inverter apparatus) together, the main terminals are conventionally screwed to a bus bar or a printed circuit board of the peripheral circuit, with the control terminals soldered thereto or connected thereto by using a connector. However, a more recent method includes steps of forming a pin terminal structure as the main terminals of the power module, mounting the power module directly on the printed circuit board of the peripheral circuit, and joining the main terminals (the pin terminals) to the circuit board by a solder flow process. The control terminals (the pin terminals) are inserted into a connector provided on the peripheral circuit. On the other hand, in the structure in FIGS. 13(a) and 13(b), the lead pins of the control terminals 4 are molded integrally with the enclosure case 2. Accordingly, to conform a length, the number, and an arrangement of the pin terminals to a user's specification or a connector specification, it is necessary to design and produce a new enclosure case integrated with terminals corresponding to the user's specification, resulting in a higher cost.
The present invention is provided in view of these points, and it is an object of the present invention to provide an improved assembled structure of a semiconductor device to solve the above problems. Also, the assembled structure has improved assembling capability and reliability while taking an advantage of the two-story building scheme, in which a power circuit and a control circuit are arranged parallel to each other in a vertical direction within a package, so that the resultant semiconductor device makes it possible to remove external lead terminals from the control circuit and replace them with good ones in order to easily accommodate the user's desired specification.
Further objects and advantages of the invention will be apparent from the following description of the invention.